The present invention concerns power supplies and, more particularly, a self-resonant power supply of the flyback type which does not require a high-voltage rectifier for supplying operating energy to a microwave oven magnetron and the like loads.
Magnetron microwave generators are becoming more widely used in food preparation appliances, such as microwave ovens and the like. The power supply utilized in many presently available microwave ovens typically utilizes a high-reactance voltage step-up transformer and a voltage doubler. Typically, a capacitance is in series between the transformer secondary winding and the load, and a voltage-doubling diode is across the anode-cathode circuit of the magnetron to provide a voltage-doubled, half-wave current supply for the magnetron. A rectified sinewave portion of operating current is applied to the magnetron at a repetition rate equal to the line frequency, e.g. 60 Hertz (Hz.). These relatively-low-frequency power supplies are of relatively great weight and require additional structural strength in the microwave appliance to protect against physical damage during shipment and use. Additionally, the typical magnetron power supply is of relatively great manufacturing cost. It is desirable to not only reduce the cost and weight of the magnetron power supply, but also to more easily control the amount of energy being supplied to the microwave-power-generating magnetron to provide greater control of the food preparation sequences achievable therewith.